FIG. 1 is a schematic diagram of a conventional apparatus 100 for compensating periodic signal in an optical disc drive. The conventional apparatus 100 includes a runout band pass compensator 102 and a servo compensator 104. There are many kinds of servo signals, such as tracking error signal, focusing error signal, and radio frequency signal, etc. Taking tracking error signal as an example, the servo compensator 104 receives the tracking error signal (Ste) and generates a tracking actuator output signal (Stc). The runout band pass compensator 102 receives also the tracking error signal (Ste) and generates a runout compensated signal (Scom) for compensating the tracking actuator output signal (Stc).
The runout band pass compensator 102 is utilized to compensate the periodic signal. Taking an example of an eccentric disk, the runout band pass compensator 102 compensates the periodic signal which results from the runout effect. However, because the band pass frequency of the runout band pass compensator 102 must be the same as the rotation frequency of the spindle motor (not shown) in the optical disc drive, it is required to design the runout band pass compensator carefully. Moreover, the conventional apparatus 100 cannot be employed for the periodic signal during a track jump of the optical disk.
In the optical disc drive, it is quite important for optical pick-up unit (OPU) to follow the track of the optical disk in order to decode the data on the disk correctly. However, due to the eccentric disk, the tracking signal will be disturbed by the periodic signal having a single frequency. Such a periodic signal due to the runout effect affects the data decoding performance disadvantageously. Consequently, there is a need to develop a control apparatus to solve the above-mentioned problems.